Effect of Density Gradient on Flame-Acoustic Interaction

摘要

Dynamic interactions between shear coaxial injector flames and periodic compression waves are investigated under controlled density ratio variations. Turbulent diffusion flames are established between an oxygen slot jet in the middle and two hydrogen slot jets on the sides, representing a sectional view of a shear coaxial injector flowfield. Transverse acoustic excitation is applied using a compression driver mounted on one side of the combustor to force possible flame-acoustic interactions. While maintaining a stoichiometric fuel-oxidizer ratio, the density of each stream is controlled by diluting the propellant gases with inert helium and argon by appropriate amounts. Results show strong dependence of flame-acoustic interaction on the density gradient between the propellants. The observed trend is consistent with the vorticity production mechanism created by the baroclinic source term in the flowfield. It is observed that the flames become more resilient to acoustic coupling when the fuel-oxidizer density difference is reduced. The results open up the possibility of using density gradient manipulations to extend the overall stability margin of shear coaxial injector flames.